In particular, elevated levels of sPD-L1 before ICI therapy, such as anti-CTLA-4 or anti-PD-1 blockade, were associated with an increased likelihood of progressive disease and unfavorable survival in different tumor settings, such as renal cell carcinoma, NSCLC, breast cancer and other solid tumors [6,8,37]. Here, PDCD1 is linked to breast cancer.